Why Is DC Power Transmission 10X More Efficient Than AC?

Actually, "insult" is a medical term that means an injury or an incident that can result in injury:

I have heard my brother in law (who is a medical researcher) use the term to describe things to which people subject their body, that eventually cause cancer or other disease.

Paul

Try my < $2/lb diet.

The UC Berkeley _Wellness Letter_ once published a letter claiming that, if it costs less than 19 cents/lb, it's healthy.

My theory was 19 cents/lb is the cost to load roots from a field onto a truck + the cost to unload the truck at a market.

In any event, it's affordable.

Bret Cahill

It is amazing how much we need to take charge of our own health, and how much doctors rely on simply treating everything with the latest pill, rather than focus on the root causes such as diet, exercise, and attitude. I have never believed in the evils of salt, but I do know some people who dump it on their food until their veggies look like snow capped mountains. There is a need for salt, as you have seen, and any sort of fanaticism in diet can be unhealthy. A friend, who is pretty much a "health food nut", told me of his latest discoveries that the body must be kept alkaline, and an excessively acid condition causes disease. See:

A possibly more scientific viewpoint is:

I once found a reference that claimed the body cannot use regular table salt for its sodium requirement, and that it must first pass through the vegetable kingdom, and be "chelated". But I'm not sure that's true:

Here's information I found about sodium:

Here is a (probably a bit wacky) pro-salt site:

I know you can do your own searches, but I found these to be interesting and informative.

HTH,

Paul

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PS: I and some friends will be doing a sing-along for disabled and elderly veterans at the Perry Point VA Hospital this Sunday. I have done this many times before, and it is a rewarding experience for them and us. I was very pleased to learn that one bedridden patient was tapping his foot to our music, and he had been largely unresponsive previously. Many of these patients no longer have family or friends to visit them and they are living out their last days in lonely isolation. It is the least I can do to spend some time entertaining them and providing some interaction with the outside world. They have given so much, and we who have benefited from their service and sacrifices must never forget them.

I thought salt doesn't react with anything in any way but first rate gourmet cook claims that salt cannot always be added after cooking and have the same effect.

Bret Cahill

Why shouldn't salt react? It dissolves easily in water and provides two very active ions. There are free (not chelated) sodium and chloride ions in your body fluids, and your body doesn't care where they came from. Chemical reactions are sensitive to temperature; things that happen quickly at cooking temperatures happen more slowly at serving temperatures, so I would expect salt in the pot to have at least slightly different effects from salt at the table. The food also spends more time in the pot or the oven than it does on your plate.

Another point about salt intake is iodine. Common salt bought in stores is 'iodized'. That is, it has a trace of the element iodine added to it. Using non-iodized salt or no salt at all and you run the risk of having a deficiency of iodine in your body. This can lead to a goiter (swelling of the thyroid) as well as other conditions.

Another good source of iodine is seafood, but if you're allergic or don't eat salt-water fish, you may need iodized salt to prevent such a dificiency.

daestrom

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| > I thought salt doesn't react with anything in any way but first rate | > gourmet cook claims that salt cannot always be added after cooking and | > have the same effect. | | Why shouldn't salt react? It dissolves easily in water and provides two | very active ions. There are free (not chelated) sodium and chloride ions | in your body fluids, and your body doesn't care where they came from. | Chemical reactions are sensitive to temperature; things that happen | quickly at cooking temperatures happen more slowly at serving | temperatures, so I would expect salt in the pot to have at least slightly | different effects from salt at the table. The food also spends more time | in the pot or the oven than it does on your plate.

Steven: Being sensible is a violation of the sci.physics manifesto.

With less than two pound feet of torque on my car's throttle, I can get greater than 100 pound feet at the drive wheel. I get more energy out of my car than I personally put in.

So I'm right and you ALL are wrong, and now I get to call you all names.

||||||||| The preceding parody was posted to make a point. |||||||||

Grow up. You are all smarter than that.

Umm, what names did you have in mind?

John

A sensitive young man such as myself should not be called really bad names.

Bret Cahill

Maybe he wants to call you good names.

Ed

Well, in your case, I think John would fit nicely. :)

Those arguing over how many angels can dance on the head of a pin know who they are. They need to come to an understanding. I'm curious about I^2R losses and the impact distributive generation (private solar etc.) would have on those line losses.

On Fri, 09 May 2008 09:05:15 -0500, OverUnity

Seems to me that a DC "local bus" should be standard within solar/wind/whatever systems; I'd suggest 400 volts DC. Then a standard, modular inverter topology could be used to connect to the grid.

John

Full wave rectified 120 VAC is still 120 V RMS (effective voltage), and 108 volts average, and 170 volts peak. But perhaps such motors are usually driven with PWM or phase-controlled SCRs or TRIACs, and 90 volts is easily produced. Motors can be driven at higher voltages for less than continuous duty cycle, so this rating allows for that as well, and it also allows for low line voltages.

DC bus voltages for use with V/F inverter drives are based on the peak voltage of the sine wave, so it is about 180, 360, and 720 VDC for common voltages of 120, 240, and 480 VAC. A DC local bus would be easy to use for either adding or taking power. There is no phase angle or waveform to contend with, and no power factor, so your watts in or out is just the voltage times the current. And there is no ELF field to cause concerns, at least on the DC bus.

This was his way to demonstrate the danger of AC, although the equivalent amount of DC may have proven just as fatal. AC has the distinction of causing fibrillation, while DC might cause your muscles to contract and make you less able to release a "hot" conductor. Here it says (for dummies) the main danger of DC is burns:

Try this powerpoint presentation (I'm still waiting on dial-up):

Here's a discussion a couple years ago:

This is pretty good:

The bottom line for electricity: "Touch Me Not!"

Paul

Half wave rectified 120 VAC is about 84 volts. 120 * .707 = 84.84 -.6 V = 84.24 VDC, unfiltered. I have seen 90 VDC motors run this way, with no speed control. When they were variable speed, a variac fed the half wave rectifier. this was in '50s and '60s equipment.